It is known that the viscosity of oils can be increased by additions of finely divided solids. Highly dispersed silica is particularly suitable for that purpose. On the other hand, additions of high-melting fats, for example, hardened glycerides of relatively long chain length, have the same effect.
In addition, additions of the above-mentioned substances may occasionally produce thixotropy phenomena. This means that the oils reduce their viscosity under shear stressing, but change back to their relatively high viscosity state after standing.
A significant synergistic effect on the viscosity behavior of oils has now surprisingly been found whereby highly dispersed silica and high-melting fats intensify one another's effectiveness to an unexpectedly high degree.